How do I alias commands in git?

Basically you just need to add lines to ~/.gitconfig

[alias]
    st = status
    ci = commit -v

Or you can use the git config alias command:

$ git config --global alias.st status 

On unix, use single quotes if the alias has a space:

$ git config --global alias.ci 'commit -v'

On windows, use double quotes if the alias has a space or a command line argument:

c:\dev> git config --global alias.ci "commit -v"

The alias command even accepts functions as parameters. Take a look at aliases.

As others have said the appropriate way to add git aliases is in your global .gitconfig file either by editing ~/.gitconfig or by using the git config --global alias.<alias> <git-command> command

Below is a copy of the alias section of my ~/.gitconfig file:

[alias]
    st = status
    ci = commit
    co = checkout
    br = branch
    unstage = reset HEAD --
    last = log -1 HEAD

Also, if you're using bash, I would recommend setting up bash completion by copying git-completion.bash to your home directory and sourcing it from your ~/.bashrc. (I believe I learned about this from the Pro Git online book.) On Mac OS X, I accomplished this with the following commands:

# Copy git-completion.bash to home directory
cp usr/local/git/contrib/completion/git-completion.bash ~/

# Add the following lines to ~/.bashrc
if [ -x /usr/local/git/bin/git ]; then
    source ~/.git-completion.bash
fi

Note: The bash completion will work not only for the standard git commands but also for your git aliases.

Finally, to really cut down on the keystrokes, I added the following to my ~/.bash_aliases file, which is sourced from ~/.bashrc:

alias gst='git status'
alias gl='git pull'
alias gp='git push'
alias gd='git diff | mate'
alias gau='git add --update'
alias gc='git commit -v'
alias gca='git commit -v -a'
alias gb='git branch'
alias gba='git branch -a'
alias gco='git checkout'
alias gcob='git checkout -b'
alias gcot='git checkout -t'
alias gcotb='git checkout --track -b'
alias glog='git log'
alias glogp='git log --pretty=format:"%h %s" --graph'